1. Field of the Invention
The present invention relates to image-forming devices. In particular, the present invention relates to a spring-assisted print media feeder apparatus for feeding print media to an image-forming device.
2. Description of the Related Art
Image-forming devices require a print media feeder apparatus to ensure a regular supply of print media. The print media feeder apparatus has an elevator tray on which the print media is loaded. The print media needs to be fed into the image-forming device at the desired position for the device to function properly. To achieve this, the elevator tray has to be moved up or down to position the top of the print media at the desired level. Usually, the elevator tray can hold a large amount of paper, for example, more than 1000 sheets. Such high-capacity elevator trays require a regular supply of power to move the elevator tray in a vertical direction. For example, an electrical motor may be used to drive the movement of the elevator tray. However, an electrical motor-driven system is expensive and requires a dedicated power supply.
To minimize the consumption of electricity, some existing high-capacity feeder apparatus use springs that are attached to the bottom of the elevator tray. These springs support the weight of the elevator tray, which is loaded with print media. However, these feeder apparatus may require a large housing and the energy stored in the spring may be released accidently and injure the user.
U.S. Pat. No. 3,937,095, titled ‘Self Adjusting Elevator’, assigned to Lincoln Manufacturing Company Incorporated, describes an apparatus for use in a storage cabinet. This apparatus uses a spring-loaded cylinder arrangement supported in a frame to maintain the frame at a desired position. However, the design of the spring-loaded cylinder arrangement makes the apparatus unsuitable for accurately adjusting the position of the frame. Moreover, this apparatus has a number of components, which makes it difficult to assemble during mass production.
U.S. Pat. No. 4,007,925, titled “Vertical rise sheet feeder,” assigned to Addressograph Multigraph Corporation, describes a movable elevator tray supported at the bottom by a plurality of springs. The height attainable by the elevator tray in the apparatus is limited by the properties of the spring. Moreover, an operator using the apparatus is susceptible to injury on the accidental release of energy stored in the spring.
In light of the foregoing, there is a need for a print media feeder apparatus that is safe from a user's perspective and does not need a dedicated power supply.